The mitochondrial genome of stygobitic sponge Eunapius subterraneus: mtDNA is highly conserved in freshwater sponges
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The complete mitochondrial DNA (mtDNA) genome of the Eunapius subterraneus (Porifera, Demospongiae), a unique stygobitic sponge, was analyzed and compared with previously published mitochondrial genomes from this group. The 24,850 bp long mtDNA genome is circular with the same gene composition as found in other metazoans. Intergenic regions (IGRs) comprise 24.7% of mtDNA and are abundant with direct and inverted repeats and palindromic elements as well as with open reading fames (ORFs) whose distribution and homology was compared with other available mt genomes with a special focus on freshwater sponges. Phylogenetic analyses based on concatenated amino acid sequences from 12 mt protein genes placed E. subterraneus in a well-supported monophyletic clade with the freshwater sponges, Ephydatia muelleri and Lubomirskia baicalensis. Our study showed high homology of mtDNA genomes among freshwater sponges, implying their recent split.
KeywordsPorifera Spongillidae Stygobitic Mitochondrial evolution
We thank Branko Jalžić and members of the Croatian Biospeleological Society for their help with specimen collection and acknowledge financial support from Croatian MSES grant 098-0982913-2478 (H. Ćetković). Prof. William R. Jeffery is gratefully acknowledged for proofreading the manuscript.
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